A study has been made on the mechanism of rosin sizing
in papermaking. By using microelectrophoresis and
laboratory prepared handsheets, a study of the effect of pH,
certain metal salts, and various physical parameters on the
overall electrokinetics and sizing efficiency of the system
has been made.
By the use of a novel sizing method it was possible to
effectively size handsheets in the alkaline pH range, which
had previously not been possible when using rosin dispersion
sizes. This permitted the inclusion of calcium carbonate as
a filler, which has particular advantages in the finished
paper. Use of the theory proposed by Derjaguin-LandauVerwey
and Overbeek on colloidal interaction, made it
possible to explain and predict the likely outcome of sizing
experiments, by analysing the electrokinetics of the system
components.
A comparative study on the effect of rosin
fortification and the stabilisation of the dispersions by
the use of casein has been made~ From the results obtained,
fortification leads to an improvement in sizing,
particularly if the drying of the paper is not very
efficient. Whereas the interactions of casein primarily
effect the stabilisation of the dispersion, protein
desorption from the solid-liquid interface causes initial
flocculation of the dispersion. If the desorption is kept
to a minimum, the dispersion is still stable and an
effective sizing agent.

Description:

A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.